Simple wireless headset production ----- Wireless Headset

Keywords: simple wireless headset The reason why I introduce this circuit is that it reflects the foundation of moderate electricity. It reflects the typical circuit of high frequency. The frequency is high, so you can exercise everyone's hands-on ability! "If the circuit is strictly calculated and experiment, the success rate of general assembly is more than 99%." Why don't you try to do one (see below), you will definitely have a sense of accomplishment, it is not bad. Give it a "wireless headset" name because it is very sensitive, when it is quiet, even the "Tick" sound of the watch will be heard. This circuit is actually a frequency modulated wireless microphone, and the circuit is divided into two parts: a part is an audio amplifier, and the other is a high frequency oscillator. The components are very good, and the method of making this wireless headset will be described below. The audio amplifier is composed of VT1, and the amplified audio signal is coupled to the high frequency oscillation circuit VT2 base by C2 (0.01uF). The high-frequency oscillation circuit VT2 operating frequency is 88-108 MHz, which is determined by the oscillation coil L1 and C4 (47P) capacitance, which is regulated by the audio signal of VT1. When the audio signal is coupled to the VT2 base, change the oscillator frequency, generate the required FM (FM) signal, and transmit to the air via antenna. When making, the microphone MIC selects high sensitivity elective microphone, and the outer casing is negative. The VT1 model is 9013h, the magnification is larger than 150, the VT2 model is 3dg 130d, the blue dot (magnification is greater than 120), f T is greater than 600MHz, which can also be replaced with 9018. L1 oscillation coil (see the right picture) With φ0.71 enamel wire on the 3mm drill round handle, then taken back. The antenna can take 1.2m soft wire, and the distance can be about 200m at this time. If the emission distance is not required, then the antenna can be used with one end 10cm wire, at which time the emission distance can be about 30m. I only experimented the post-type method, which can achieve the expected effect, but the stability of the antenna is very affected by the stability of the frequency, and the experiment has been directly soldered directly on the circuit board to do the antenna effect. When operating properly, the circuit current is about 5 mA. When the power supply voltage is different, the entire machine is different. When debugging, use a FM radio to receive. Pull open about 5-10m, generally receive the sound delivered by the transmitter, and can be tested close to the microphone with a mechanical watch. If the signal is not received, the spacing of L1 can be slightly adjusted, or the capacity of the 47P capacitor can be reduced. Adjusting R1 can adjust the sensitivity of the microphone. how about it? Happy! Increase the power, you can also make a small FM launcher.